The present invention relates to an air induction system of an internal-combustion engine, and more particularly, to an air induction system for a multi-cylinder engine, having at least one air collector which is connected to individual cylinders of the internal-combustion engine.
German Patent No. DE- 38 20 674 Al shows an air induction system in which the length of individual intake pipes can be varied continuously by the telescope-type moving-in and moving-out of pipe elbows guided in stationary intake manifolds. During a low rotational speed of the internal-combustion engine, these individual intake pipes have their maximal length and their inlet openings rest against an interior wall of a suction distributor which surrounds the pipe elbows. In this position, the suction distributor supplies air to the individual intake pipes by way of a pipe connected thereto. When the rotational speed rises, the pipe elbows are swivelled into the intake manifolds so that the inlet openings lift off the interior wall and the individual intake pipes take in directly from the suction distributor.
It is an object of the present invention to provide an air intake system for an internal-combustion engine in which the length of the pipes, which guide the air to the cylinders, is to be varied in a simple manner, with a required installation space as small as possible and a simple mounting.
This object has been achieved in accordance with the present invention by holding pipe elbows in the air collector openly on a stationary shaft so that they can be swivelled into positions, in one of which one outlet opening of the pipe elbow rests directly on an inlet opening of the intake manifold.
This open arrangement of pipe elbows on a stationary shaft, permits the coupling of the pipe elbows to the intake manifolds by a simple swivel movement by virtue of which the intake path taken by the air is changed. In the first position, an outlet opening of the pipe elbow is disposed directly on an inlet opening of an intake manifold so that the intake path from the air collector to the cylinders of the internal-combustion engine is formed by the series connection of the intake manifolds and the pipe elbows. In a second position, the two openings are arranged at a distance of one another, such that the intake manifolds take in directly from the air collector.
The swivel movement requires little actuating power because the shaft penetrates the bearings assigned to the pipe elbows almost in the mass center of gravity of the pipe elbows; in this case, the pipe elbows only tilt about their center of gravity. The moment of inertia is therefore minimized, and the control element triggering the swivel movement may be dimensioned to be relatively small. The friction to be overcome by the control element is determined only by the friction occurring in the bearing blocks holding the shaft, since the pipe elbows themselves are not disposed in any type of guide bushes with friction.
Vibrations, caused by the induction strokes of the internal-combustion engine, as well as vibrations transmitted by mechanical excitation, have only a slight effect on the pipe elbows. This is because, by virtue of the shaft, the pipe elbows are mechanically coupled to the air collector only at a few points, and this shaft is disposed in a junction plane which carries out only slight tilts about the longitudinal axis of the shaft. Torques are thus not transmitted to the shaft.
The development of the pipes, which can be coupled to the intake manifolds, as pipe elbows, and a lid, which extends closely adjacent to the pipe elbows, permit a small installation space. Together with the above-mentioned advantages, this arrangement has the result that the air induction system can be used on different internalcombustion engines in different installed positions. The junction plane between the housing parts of the air collector, as far as its position with respect to the internal-combustion engine is concerned, may extend horizontally or vertically or in a position which is situated in-between. In addition, this air induction system ma be used on internal-combustion engines with an in-line or a V-shaped cylinder arrangement.
Since the air collector comprises essentially only two housing parts, in the junction plane of which the shaft is held in bearing blocks constructed in one piece with outside walls of these housing parts, a fast and simple mounting and dismounting of this air induction system is possible.